Currently, in an evolved packet network (EPS, Evolved Packet System), if an MME (Mobility Management Entity, mobility management entity) or an SGSN (Serving GPRS Support Node, serving GPRS support node) is faulty, the MME/SGSN may lose a context of the served UE (User Equipment, user equipment). In this case, if an SGW (Serving Gateway, serving gateway) perceives the fault of the MME/SGSN, the SGW may delete the context of the UE served by the faulty MME/SGSN. In this way, when receiving, from the PGW (Packet Data Network Gateway, packet data network gateway), downlink data about the UE served by the faulty MME/SGSN, the SGW may not reselect a mobility management element, may not be able to re-create a context for the UE, and may not provide services for the UE, which affects user experience.